Spare tires for vehicles are mostly heavy and bulky objects that, in many vehicles, are accommodated below the vehicle body and are secured against the bottom of the vehicle or against a structure carried by elements of the vehicle chassis. Because of their weight and size, vehicle spare tires can rarely be lowered to the ground, nor raised for storage, by hand. For this reason, heavier vehicles are provided with hoisting devices such as winches, by means of which the spare tire is lowered or raised using a steel cable.
Steel cables, however, are liable to snap or break due to a number of causes, all of which are relevant to their use for the above-mentioned purpose: lack of maintenance, corrosion due to exposure to the environment, fatigue due to vibration-enhanced stresses, accidents, crashes, severe shocks, and the like. A hoisting cable failure could cause the spare tire to break loose from the vehicle and should this happen, it would seriously endanger other road users behind or alongside it.
A safety device to prevent such accidents is known from U.S. Pat. No. 5,975,498, which provides a device consisting of an additional short cable. In case of main cable failure, the additional cable prevents the tire from breaking loose. However, the device functions well only when the main cable breaks near the object end.
U.S. Pat. No. 6,406,000 in the name of the present assignee discloses a device for securing an upper terminal position of a liftable and lowerable object such a spare tire secured by a cable, wherein a lever and catch mechanism operate to prevent the tire from falling in the event of the cable snapping.